Aqueous concentrate formulations of pesticidal and plant growth modifying chemicals are widely used in agricultural, industrial, recreational and residential areas worldwide. The active ingredients of such concentrates are frequently carboxylic acids, more particularly their salts. An aqueous concentrate is essentially a solution of the active ingredient in water at relatively high concentration, intended for dilution in water prior to application by spraying or other means. Typically the aqueous concentrate is diluted with about 10 to about 100 times its own volume of water prior to application.
Many herbicidal carboxylic acids such as, for example, the phenoxycarboxylic acids like 2,4-D, 2,4-DB, MCPA, MCPB, mecopropand clomeprop, the benzoic acids like dicamba and chloramben, the picolinic acids like aminopyralid, picloram and clopyralid, the pyridinyloxyacetic acids like triclopyr and fluoroxypyr, and the quinolinecarboxylic acids like quinclorac and quinmerac are relatively insoluble in water in the acid form. Therefore, these herbicides are in many instances formulated as aqueous concentrates of water soluble salts. Commonly used salts of these herbicidal carboxylic acids used for preparing aqueous herbicide concentrates include, for example, ammonium, iso-propyl ammonium, dimethyl ammonium, triethyl ammonium, monoethanol ammonium, diethanol ammonium, triethanol ammonium, triisopropanol ammonium and the like, which are collectively referred herein as the ammonium salts.
The disadvantage of using ammonium salts of herbicidal carboxylic acids to prepare aqueous herbicide concentrates is that they can be irritating if accidentally splashed or otherwise injected into the eye of anyone handling such a formulation. This property may lead to restrictive labeling of the products that limits their usefulness in certain markets, even where the active ingredient itself provides no such hazard.
Choline is an essential nutrient for mammals, necessary for optimal health based on the Dietary Reference Intakes recommended by the National Academy of Sciences. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation and a counterion X− such as, for example, chloride (choline chloride), hydroxide (choline hydroxide) or tartrate (choline tartrate).
Choline hydroxide can be mixed with 2,4-D in water and readily forms the choline salt of 2,4-D which has the structure
and readily forms a water soluble concentrate. This concentrate, when diluted in water and applied postemergently to susceptible plants, provides good weed control as disclosed in WO 2008/106107 A1.
It would be desirable to have an herbicidal carboxylic acid derivative that is at least as active as the commercially used carboxylic acid herbicide salts and highly soluble in water, but which is less irritating to eyes and therefore safer to use for those who handle and apply it.